Assuming I have the following URL: /members/some/path/route
I want a regex that will return only /some/path/route
So far I have [^\/]\/.*
But that doesn't quite work as it returns s/some/path/route
Can someone give me a hand here? I'd also like it if someone can tell me why my regex doesn't quite work so I can learn why it doesn't work.
I'm using ruby.
Assuming you are using javascript:
your regex will be
result = url.match(/(?:\/.*?)(\/.*)/g);
and your expected string will be held in result[1]
If using RUBY
if url =~ /(?:\/.*?)(\/.*)/
result = $~[1]
end
OR
regexp = /(?:\/.*?)(\/.*)/
match = regexp.match(url)
if match
result = match[1]
else
result = ""
end
You need to find the second "/" and take the rest
preg_match("/\/(.*?)(\/.*)/", $url, $preg);
print_r($preg);
returns
Array
(
[0] => /members/some/path/route
[1] => members
[2] => /some/path/route
)
But, I recommend not using RegExp, since it is a simple string, an explode() function would do
$path_array = array_slice(explode("/", $url), 2); // we are slicing at 2, because there is a leading '/' at the beginning
$new_path = "/".implode("/", $path_array);
echo $new_path;
I would not use a regex for this. Instead I would use Pathname#each_filename to construct an array whose elements are each component of the path.
str = "/members/some/path/route"
require "pathname"
Pathname(str).each_filename.to_a[1..-1].join('/')
#=> "some/path/route"
We see that:
Pathname(str).each_filename.to_a[1..-1]
#=> ["members", "some", "path", "route"]
This uses the class method Kernel::Pathname. I don't find the doc for that (which would be with the docs for Object), but we can verify:
method(:Pathname).owner
#=> Kernel
This is similar to the class methods Kernel::Array, Kernel::String and others:
Array(21) # => [21]
String(19) # => "19"
You could instead write:
Pathname.new(str).each_filename.to_a[1..-1].join('/')
#=> "some/path/route"
Related
What's the easiest way in Ruby to interchange a part of a string with another value. Let's say that I have an email, and I want to check it on two domains, but I don't know which one I'll get as an input. The app I'm building should work with #gmail.com and #googlemail.com domains.
Example:
swap_string 'user#gmail.com' # >>user#googlemail.com
swap_string 'user#googlemail.com' # >>user#gmail.com
If you're looking to substitute a part of a string with something else, gsub works quite well.
Link to Gsub docs
It lets you match a part of a string with regex, and then substitute just that part with another string. Naturally, in place of regex, you can just use a specific string.
Example:
"user#gmail.com".gsub(/#gmail/, '#googlemail')
is equal to
user#googlemail.com
In my example I used #gmail and #googlemail instead of just gmail and googlemail. The reason for this is to make sure it's not an account with gmail in the name. It's unlikely, but could happen.
Don't match the .com either, as that can change depending on where the user's email is.
Assuming googlemail.com and gmail.com are the only two possibilities, you can use sub to replace a pattern with given replacement:
def swap_string(str)
if str =~ /gmail.com$/
str.sub("gmail.com","googlemail.com")
else
str.sub("googlemail.com","gmail.com")
end
end
swap_string 'user#gmail.com'
# => "user#googlemail.com"
swap_string 'user#googlemail.com'
# => "user#gmail.com"
You can try with Ruby gsub :
eg:
"user#gmail.com".gsub("gmail.com","googlemail.com");
As per your need of passing a string parameter in a function this should do:
def swap_mails(str)
if str =~ /gmail.com$/
str.sub('gmail.com','googlemail.com');
else
str.sub('googlemail.com','gmail.com');
end
end
swap_mails "vgmail#gmail.com" //vgmail#googlemail.com
swap_mails "vgmail#googlemail.com" ////vgmail#gmail.com
My addition :
def swap_domain str
str[/.+#/] + [ 'gmail.com', 'googlemail.com' ].detect do |d|
d != str.split('#')[1]
end
end
swap_domain 'user#gmail.com'
#=> user#googlemail.com
swap_domain 'user#googlemail.com'
#=> user#gmail.com
And this is bad code, imo.
String has a neat trick up it's sleeve in the form of String#[]:
def swap_string(string, lookups = {})
string.tap do |s|
lookups.each { |find, replace| s[find] = replace and break if s[find] }
end
end
# Example Usage
lookups = {"googlemail.com"=>"gmail.com", "gmail.com"=>"googlemail.com"}
swap_string("user#gmail.com", lookups) # => user#googlemail.com
swap_string("user#googlemail.com", lookups) # => user#gmail.com
Allowing lookups to be passed to your method makes it more reusable but you could just as easily have that hash inside of the method itself.
I need to get the expected output in ruby by using any method like scan or match.
Input string:
"http://test.com?t&r12=1&r122=1&r1=1&r124=1"
"http://test.com?t&r12=1&r124=1"
Expected:
r12=1,r122=1, r1=1, r124=1
r12=1,r124=1
How can I get the expected output using regex?
Use regex /r\d+=\d+/:
"http://test.com?t&r12=1&r122=1&r1=1&r124=1".scan(/r\d+=\d+/)
# => ["r12=1", "r122=1", "r1=1", "r124=1"]
"http://test.com?t&r12=1&r124=1".scan(/r\d+=\d+/)
# => ["r12=1", "r124=1"]
You can use join to get a string output. Here:
"http://test.com?t&r12=1&r122=1&r1=1&r124=1".scan(/r\d+=\d+/).join(',')
# => "r12=1,r122=1,r1=1,r124=1"
Update
If the URL contains other parameters that may include r in end, the regex can be made stricter:
a = []
"http://test.com?r1=2&r12=1&r122=1&r1=1&r124=1&ar1=2&tr2=3&xy4=5".scan(/(&|\?)(r+\d+=\d+)/) {|x,y| a << y}
a.join(',')
# => "r12=1,r122=1,r1=1,r124=1"
While input strings are urls with queries, I would safeguard myself from the false positives:
input = "http://test.com?t&r12=1&r122=1&r1=1&r124=1"
query_params = input.split('?').last.split('&')
#⇒ ["t", "r12=1", "r122=1", "r1=1", "r124=1"]
r_params = query_params.select { |e| e =~ /\Ar\d+=\d+/ }
#⇒ ["r12=1", "r122=1", "r1=1", "r124=1"]
r_params.join(',')
#⇒ "r12=1,r122=1,r1=1,r124=1"
It’s safer than just scan the original input for any regexp.
If you really need to do it with regex correctly, you'll need to use a regex like this:
puts "http://test.com?t&r12=1&r122=1&r1=1&r124=1".scan(/(?:http.*?\?t|(?<!^)\G)\&*(\br\d*=\d*)(?=.*$)/i).join(',')
puts "http://test.com?t&r12=1&r124=1".scan(/(?:http.*?\?t|(?<!^)\G)\&*(\br\d*=\d*)(?=.*$)/i).join(',')
Sample program output:
r12=1,r122=1,r1=1,r124=1
r12=1,r124=1
I have a string:
s="123--abc,123--abc,123--abc"
I tried using Ruby 1.9's new feature "named groups" to fetch all named group info:
/(?<number>\d*)--(?<chars>\s*)/
Is there an API like Python's findall which returns a matchdata collection? In this case I need to return two matches, because 123 and abc repeat twice. Each match data contains of detail of each named capture info so I can use m['number'] to get the match value.
Named captures are suitable only for one matching result.
Ruby's analogue of findall is String#scan. You can either use scan result as an array, or pass a block to it:
irb> s = "123--abc,123--abc,123--abc"
=> "123--abc,123--abc,123--abc"
irb> s.scan(/(\d*)--([a-z]*)/)
=> [["123", "abc"], ["123", "abc"], ["123", "abc"]]
irb> s.scan(/(\d*)--([a-z]*)/) do |number, chars|
irb* p [number,chars]
irb> end
["123", "abc"]
["123", "abc"]
["123", "abc"]
=> "123--abc,123--abc,123--abc"
Chiming in super-late, but here's a simple way of replicating String#scan but getting the matchdata instead:
matches = []
foo.scan(regex){ matches << $~ }
matches now contains the MatchData objects that correspond to scanning the string.
You can extract the used variables from the regexp using names method. So what I did is, I used regular scan method to get the matches, then zipped names and every match to create a Hash.
class String
def scan2(regexp)
names = regexp.names
scan(regexp).collect do |match|
Hash[names.zip(match)]
end
end
end
Usage:
>> "aaa http://www.google.com.tr aaa https://www.yahoo.com.tr ddd".scan2 /(?<url>(?<protocol>https?):\/\/[\S]+)/
=> [{"url"=>"http://www.google.com.tr", "protocol"=>"http"}, {"url"=>"https://www.yahoo.com.tr", "protocol"=>"https"}]
#Nakilon is correct showing scan with a regex, however you don't even need to venture into regex land if you don't want to:
s = "123--abc,123--abc,123--abc"
s.split(',')
#=> ["123--abc", "123--abc", "123--abc"]
s.split(',').inject([]) { |a,s| a << s.split('--'); a }
#=> [["123", "abc"], ["123", "abc"], ["123", "abc"]]
This returns an array of arrays, which is convenient if you have multiple occurrences and need to see/process them all.
s.split(',').inject({}) { |h,s| n,v = s.split('--'); h[n] = v; h }
#=> {"123"=>"abc"}
This returns a hash, which, because the elements have the same key, has only the unique key value. This is good when you have a bunch of duplicate keys but want the unique ones. Its downside occurs if you need the unique values associated with the keys, but that appears to be a different question.
If using ruby >=1.9 and the named captures, you could:
class String
def scan2(regexp2_str, placeholders = {})
return regexp2_str.to_re(placeholders).match(self)
end
def to_re(placeholders = {})
re2 = self.dup
separator = placeholders.delete(:SEPARATOR) || '' #Returns and removes separator if :SEPARATOR is set.
#Search for the pattern placeholders and replace them with the regex
placeholders.each do |placeholder, regex|
re2.sub!(separator + placeholder.to_s + separator, "(?<#{placeholder}>#{regex})")
end
return Regexp.new(re2, Regexp::MULTILINE) #Returns regex using named captures.
end
end
Usage (ruby >=1.9):
> "1234:Kalle".scan2("num4:name", num4:'\d{4}', name:'\w+')
=> #<MatchData "1234:Kalle" num4:"1234" name:"Kalle">
or
> re="num4:name".to_re(num4:'\d{4}', name:'\w+')
=> /(?<num4>\d{4}):(?<name>\w+)/m
> m=re.match("1234:Kalle")
=> #<MatchData "1234:Kalle" num4:"1234" name:"Kalle">
> m[:num4]
=> "1234"
> m[:name]
=> "Kalle"
Using the separator option:
> "1234:Kalle".scan2("#num4#:#name#", SEPARATOR:'#', num4:'\d{4}', name:'\w+')
=> #<MatchData "1234:Kalle" num4:"1234" name:"Kalle">
I needed something similar recently. This should work like String#scan, but return an array of MatchData objects instead.
class String
# This method will return an array of MatchData's rather than the
# array of strings returned by the vanilla `scan`.
def match_all(regex)
match_str = self
match_datas = []
while match_str.length > 0 do
md = match_str.match(regex)
break unless md
match_datas << md
match_str = md.post_match
end
return match_datas
end
end
Running your sample data in the REPL results in the following:
> "123--abc,123--abc,123--abc".match_all(/(?<number>\d*)--(?<chars>[a-z]*)/)
=> [#<MatchData "123--abc" number:"123" chars:"abc">,
#<MatchData "123--abc" number:"123" chars:"abc">,
#<MatchData "123--abc" number:"123" chars:"abc">]
You may also find my test code useful:
describe String do
describe :match_all do
it "it works like scan, but uses MatchData objects instead of arrays and strings" do
mds = "ABC-123, DEF-456, GHI-098".match_all(/(?<word>[A-Z]+)-(?<number>[0-9]+)/)
mds[0][:word].should == "ABC"
mds[0][:number].should == "123"
mds[1][:word].should == "DEF"
mds[1][:number].should == "456"
mds[2][:word].should == "GHI"
mds[2][:number].should == "098"
end
end
end
I really liked #Umut-Utkan's solution, but it didn't quite do what I wanted so I rewrote it a bit (note, the below might not be beautiful code, but it seems to work)
class String
def scan2(regexp)
names = regexp.names
captures = Hash.new
scan(regexp).collect do |match|
nzip = names.zip(match)
nzip.each do |m|
captgrp = m[0].to_sym
captures.add(captgrp, m[1])
end
end
return captures
end
end
Now, if you do
p '12f3g4g5h5h6j7j7j'.scan2(/(?<alpha>[a-zA-Z])(?<digit>[0-9])/)
You get
{:alpha=>["f", "g", "g", "h", "h", "j", "j"], :digit=>["3", "4", "5", "5", "6", "7", "7"]}
(ie. all the alpha characters found in one array, and all the digits found in another array). Depending on your purpose for scanning, this might be useful. Anyway, I love seeing examples of how easy it is to rewrite or extend core Ruby functionality with just a few lines!
A year ago I wanted regular expressions that were more easy to read and named the captures, so I made the following addition to String (should maybe not be there, but it was convenient at the time):
scan2.rb:
class String
#Works as scan but stores the result in a hash indexed by variable/constant names (regexp PLACEHOLDERS) within parantheses.
#Example: Given the (constant) strings BTF, RCVR and SNDR and the regexp /#BTF# (#RCVR#) (#SNDR#)/
#the matches will be returned in a hash like: match[:RCVR] = <the match> and match[:SNDR] = <the match>
#Note: The #STRING_VARIABLE_OR_CONST# syntax has to be used. All occurences of #STRING# will work as #{STRING}
#but is needed for the method to see the names to be used as indices.
def scan2(regexp2_str, mark='#')
regexp = regexp2_str.to_re(mark) #Evaluates the strings. Note: Must be reachable from here!
hash_indices_array = regexp2_str.scan(/\(#{mark}(.*?)#{mark}\)/).flatten #Look for string variable names within (#VAR#) or # replaced by <mark>
match_array = self.scan(regexp)
#Save matches in hash indexed by string variable names:
match_hash = Hash.new
match_array.flatten.each_with_index do |m, i|
match_hash[hash_indices_array[i].to_sym] = m
end
return match_hash
end
def to_re(mark='#')
re = /#{mark}(.*?)#{mark}/
return Regexp.new(self.gsub(re){eval $1}, Regexp::MULTILINE) #Evaluates the strings, creates RE. Note: Variables must be reachable from here!
end
end
Example usage (irb1.9):
> load 'scan2.rb'
> AREA = '\d+'
> PHONE = '\d+'
> NAME = '\w+'
> "1234-567890 Glenn".scan2('(#AREA#)-(#PHONE#) (#NAME#)')
=> {:AREA=>"1234", :PHONE=>"567890", :NAME=>"Glenn"}
Notes:
Of course it would have been more elegant to put the patterns (e.g. AREA, PHONE...) in a hash and add this hash with patterns to the arguments of scan2.
Piggybacking off of Mark Hubbart's answer, I added the following monkey-patch:
class ::Regexp
def match_all(str)
matches = []
str.scan(self) { matches << $~ }
matches
end
end
which can be used as /(?<letter>\w)/.match_all('word'), and returns:
[#<MatchData "w" letter:"w">, #<MatchData "o" letter:"o">, #<MatchData "r" letter:"r">, #<MatchData "d" letter:"d">]
This relies on, as others have said, the use of $~ in the scan block for the match data.
I like the match_all given by John, but I think it has an error.
The line:
match_datas << md
works if there are no captures () in the regex.
This code gives the whole line up to and including the pattern matched/captured by the regex. (The [0] part of MatchData) If the regex has capture (), then this result is probably not what the user (me) wants in the eventual output.
I think in the case where there are captures () in regex, the correct code should be:
match_datas << md[1]
The eventual output of match_datas will be an array of pattern capture matches starting from match_datas[0]. This is not quite what may be expected if a normal MatchData is wanted which includes a match_datas[0] value which is the whole matched substring followed by match_datas[1], match_datas[[2],.. which are the captures (if any) in the regex pattern.
Things are complex - which may be why match_all was not included in native MatchData.
I have strings like this:
"/detail/205193-foo-var-bar-foo.html"
"/detail/183863-parse-foo.html"
"/detail/1003-bar-foo-bar.html"
How to get ids (205193, 183863, 1003) from it with Ruby?
Just say s[/\d+/]
[
"/detail/205193-foo-var-bar-foo.html",
"/detail/183863-parse-foo.html",
"/detail/1003-bar-foo-bar.html"
].each { |s| puts s[/\d+/] }
could also do something like this
"/detail/205193-foo-var-bar-foo.html".gsub(/\/detail\//,'').to_i
=> 205193
regex = /\/detail\/(\d+)-/
s = "/detail/205193-foo-var-bar-foo.html"
id = regex.match s # => <MatchData "/detail/205193-" 1:"205193">
id[1] # => "205193"
$1 # => "205193"
The MatchData object will store the entire matched portion of the string in the first element, and any matched subgroups starting from the second element (depending on how many matched subgroups there are)
Also, Ruby provides a shortcut to the most recent matched subgroup with $1 .
One easy way to do it would be to strip out the /detail/ part of your string, and then just call to_i on what's left over:
"/detail/1003-bar-foo-bar.html".gsub('/detail/','').to_i # => 1003
s = "/detail/205193-foo-var-bar-foo.html"
num = (s =~ /detail\/(\d+)-/) ? Integer($1) : nil
I want to replace the last occurrence of a substring in Ruby. What's the easiest way?
For example, in abc123abc123, I want to replace the last abc to ABC. How do I do that?
How about
new_str = old_str.reverse.sub(pattern.reverse, replacement.reverse).reverse
For instance:
irb(main):001:0> old_str = "abc123abc123"
=> "abc123abc123"
irb(main):002:0> pattern="abc"
=> "abc"
irb(main):003:0> replacement="ABC"
=> "ABC"
irb(main):004:0> new_str = old_str.reverse.sub(pattern.reverse, replacement.reverse).reverse
=> "abc123ABC123"
"abc123abc123".gsub(/(.*(abc.*)*)(abc)(.*)/, '\1ABC\4')
#=> "abc123ABC123"
But probably there is a better way...
Edit:
...which Chris kindly provided in the comment below.
So, as * is a greedy operator, the following is enough:
"abc123abc123".gsub(/(.*)(abc)(.*)/, '\1ABC\3')
#=> "abc123ABC123"
Edit2:
There is also a solution which neatly illustrates parallel array assignment in Ruby:
*a, b = "abc123abc123".split('abc', -1)
a.join('abc')+'ABC'+b
#=> "abc123ABC123"
Since Ruby 2.0 we can use \K which removes any text matched before it from the returned match. Combine with a greedy operator and you get this:
'abc123abc123'.sub(/.*\Kabc/, 'ABC')
#=> "abc123ABC123"
This is about 1.4 times faster than using capturing groups as Hirurg103 suggested, but that speed comes at the cost of lowering readability by using a lesser-known pattern.
more info on \K: https://www.regular-expressions.info/keep.html
Here's another possible solution:
>> s = "abc123abc123"
=> "abc123abc123"
>> s[s.rindex('abc')...(s.rindex('abc') + 'abc'.length)] = "ABC"
=> "ABC"
>> s
=> "abc123ABC123"
When searching in huge streams of data, using reverse will definitively* lead to performance issues. I use string.rpartition*:
sub_or_pattern = "!"
replacement = "?"
string = "hello!hello!hello"
array_of_pieces = string.rpartition sub_or_pattern
( array_of_pieces[(array_of_pieces.find_index sub_or_pattern)] = replacement ) rescue nil
p array_of_pieces.join
# "hello!hello?hello"
The same code must work with a string with no occurrences of sub_or_pattern:
string = "hello_hello_hello"
# ...
# "hello_hello_hello"
*rpartition uses rb_str_subseq() internally. I didn't check if that function returns a copy of the string, but I think it preserves the chunk of memory used by that part of the string. reverse uses rb_enc_cr_str_copy_for_substr(), which suggests that copies are done all the time -- although maybe in the future a smarter String class may be implemented (having a flag reversed set to true, and having all of its functions operating backwards when that is set), as of now, it is inefficient.
Moreover, Regex patterns can't be simply reversed. The question only asks for replacing the last occurrence of a sub-string, so, that's OK, but readers in the need of something more robust won't benefit from the most voted answer (as of this writing)
You can achieve this with String#sub and greedy regexp .* like this:
'abc123abc123'.sub(/(.*)abc/, '\1ABC')
simple and efficient:
s = "abc123abc123abc"
p = "123"
s.slice!(s.rindex(p), p.size)
s == "abc123abcabc"
string = "abc123abc123"
pattern = /abc/
replacement = "ABC"
matches = string.scan(pattern).length
index = 0
string.gsub(pattern) do |match|
index += 1
index == matches ? replacement : match
end
#=> abc123ABC123
I've used this handy helper method quite a bit:
def gsub_last(str, source, target)
return str unless str.include?(source)
top, middle, bottom = str.rpartition(source)
"#{top}#{target}#{bottom}"
end
If you want to make it more Rails-y, extend it on the String class itself:
class String
def gsub_last(source, target)
return self unless self.include?(source)
top, middle, bottom = self.rpartition(source)
"#{top}#{target}#{bottom}"
end
end
Then you can just call it directly on any String instance, eg "fooBAR123BAR".gsub_last("BAR", "FOO") == "fooBAR123FOO"
.gsub /abc(?=[^abc]*$)/, 'ABC'
Matches a "abc" and then asserts ((?=) is positive lookahead) that no other characters up to the end of the string are "abc".